Auto-scroll to the first invalid form field.

[Octobug]

Is your enhancement request related to a problem? Please describe

You fill some fields, scroll to the bottom of a page, and click the "Post your question". But nothing happened. You realize that you must have forgotten filling some fields, so you scroll back by yourself. This is a bit annoying especially on a 'short' screen.

Describe the solution you'd like

When there is still an invalid form field out of the viewport (or no matter it is in the viewport or not), Answer auto-scrolls to that field for the user. If there are multiple invalid fields, it scrolls to the first one.

Describe alternatives you've considered

Or at least, the UI pop up something to click for the user. Then the clicking trigger the auto-scrolling.